This disclosure relates to a gas turbine engine airfoil component temperature control system and method used during engine operation.
Gas turbine engines typically include a compressor section, a combustor section and a turbine section. During operation, air is pressurized in the compressor section and is mixed with fuel and burned in the combustor section to generate hot combustion gases. The hot combustion gases are communicated through the turbine section, which extracts energy from the hot combustion gases to power the compressor section and other gas turbine engine loads.
Both the compressor and turbine sections may include alternating series of rotating blades and stationary vanes that extend into the core flow path of the gas turbine engine. For example, in the turbine section, turbine blades rotate and extract energy from the hot combustion gases that are communicated along the core flow path of the gas turbine engine. The turbine vanes, which generally do not rotate, guide the airflow and prepare it for the next set of blades.
The radial temperature distribution of the high pressure turbine of any gas turbine engine is important in determining the life of the turbine. The stress and creep experienced by the blade is determined by the radial forces due to rotation and the radial temperature distribution on the turbine blade, particularly at high power conditions. The exact gas temperature distribution exiting the combustor and heating the turbine blades is extremely difficult to ascertain exactly and under all conditions. The blades are difficult to instrument because they are rotating. Gas temperatures in modern turbines can exceed the melting temperature of nearly all metallic materials. As such, the temperature is estimated from measurements conducted in rig tests and with computational methods. Any measurements that can be made (such as paint discoloration tests) are indicative of peak average temperature. These measurements are indicative of a particular set of hardware which was used for the test. It cannot predict the exact temperature for all combinations of hardware that are assembled in production, and, as such, safety factors must be applied to limit the maximum gas temperature to be used in production. The low allowable temperature results in reduced engine fuel efficiency.
Radial temperature profiles are developed as part of combustor development programs where combustor air flow distribution is designed to produce a radial temperature distribution necessitated by the turbine stress limitations. The success of the combustor design is again limited to the degree to which the gas temperatures actually convert to turbine blade temperatures with the individual cooling schemes, the degree to which the combustor and fuel nozzle hardware are representative of the future production field, and to the extent that static temperature field measurements are indicative of transient distributions found in the field with different degrees of hardware deterioration.